# What is Voltage regulator: Definition and 68 Discussions

A voltage regulator is a system designed to automatically maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.

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1. ### Automatic Voltage regulator rating

Hello Everyone, I'm here in a country which has a 220v single phase. My wife's \$700 Microwave/Convection oven just arrived from the US. The rating of this appliance is: 110v, 1750 watts, 15 amperes. I've talked to suppliers here and was told to buy an AVR with a rating(wattage) 5 times more of...
2. ### Load resistance in voltage regulator

Homework Statement [/B] I want to find the minimum resistance ##R_L## so as to maintain ##V_z##(voltage of the zener corresponding to the minimum current ##I_{z_0}##) across the same resistor ##R_L##. Homework Equations ##V_z##(voltage of the zener corresponding to the minimum current...
3. ### Is this a good GM tube voltage regulator and rectifier?

https://www.circuit-diagram.org/editor/ Hi, I was wondering if this is a good voltage rectifier and regulator for a GM tube power supply? The AC supply is approximately 500V, and the strange component at the bottom is a voltage regulator tube. Seems to work OK but I don't have any test equipment...
4. ### Ground current for a voltage regulator

Homework Statement Homework Equations 3. The Attempt at a Solution [/B] Currently working on the question relating to the ground current on the voltage regulator, 7805 (data sheet included below) I am very much unsure what to calculate here I'm assuming the current to ground is the input...
5. ### Queries related to buck converters

In a circuit that I am building, I have a rectified DC of about 22V, and I want to regulate this down to say, around 8V to 10V. Previously, I thought of using a voltage regulator, LM7808, as discussed here, but I strongly believe that a potential drop of 22V - 10V = 12V would produce a lot of...
6. ### How does a voltage regulator differ from a zener diode?

I am making a circuit with Arduino. It is known that the recommended power supply of an Arduino is 7V - 12V. I am going to use a 9-0-9 (230V to 9V) transformer, convert the stepped down voltage to DC, and feed it into the Arduino through the Vin pin. Now, there are chances that the input AC may...
7. ### Car reading 17V+ in the battery when running, how to fix?

Hi, I have a 2004 Toyota Matrix with 270 000km. It's working great but today when i started my car the battery was going up to 17.2V (i have a battery voltage reader in the car at all time). It's the first time it went up there, it usually stays in the 13-14V. I know something is wrong and I...
8. ### Understanding Dual Output Zener PSU

I am struggling to understand the voltages present in the circuit below. So as stated in the diagram, there is 30V AC at the secondary of the transformer, this is equivalent of 42.4Vpeak. The bridge rectifier changes this to DC and drops the voltage down to roughly 26.3Vpeak DC where each diode...
9. ### Is the STMicroelectronics L7912CV Voltage Regulator Suitable for a +12V Output?

[mod note: thread moved from homework forum] I have this Mouser voltage regulator https://www.mouser.com/ProductDetail/STMicroelectronics/L7912CV/?qs=sGAEpiMZZMug9GoBKXZ75xbXFDWiKqpmvrbz5I0HaKg%3D Wired according to datasheet https://www.mouser.com/ds/2/389/l79-974159.pdf see insert photo...
10. ### Need help with voltage regulator circuit that uses 7805

Well let me explain. I've finished a circuit that consists in a microcontroller unit (in this case a PIC16F877A) that is connected to a LCD module, a keyboard and a RTC module (via I2C protocol). As far as I know all of them require VCC (=+5V) for operating so I needed to create a +5V regulated...
11. ### Voltage Regulator Circuit Calculations

Hey Guys, so I'm just in need of some help in relation to finding the output current after the voltage has been dropped to 6V. The circuit has an input voltage of 24V and I've attached a photo of my circuit diagram. Hopefully I haven't made any errors in that, but I've tested the circuit and it...
12. ### Increasing voltage regulator current

I'm looking to draw about 6A. I have an LM338 regulator that can supply up to 5A. Searching the internet I came across this schematic, So basically when the 1R resistor drops 0.6V then the transistor conducts the remainder of the current. I calculated my own values for those two resistors. Was...
13. ### LDO voltage regulator stability

I haven't done any Bode plots before, and so I'm reading about LDO stability and I came across this file, which I am trying to understand: http://www.ti.com/lit/an/slyt194/slyt194.pdf Under the stability analysis, it names the poles and zeroes. How are these calculated? I assume that the...

Homework Statement [/B] Calculate the output voltage range for the adjustable voltage regulator circuit shown in FIGURE 1. I have read an older post and have understood how the formula works but I am thrown off by the inclusion of the 50uA current coming from the Adjust Pin. How would I...
15. ### How Can an Op-Amp and Diode be Used to Convert 12V to 5V for a PIR Detector?

Homework Statement FIGURE 3 (on page 7) shows a PIR (passive infra-red) detector and its associated amplifier, as used in burglar alarm systems1. (a) The detector is powered from a 12 V unregulated supply that needs to be stepped down to 5 V. Design a suitable 12-to-5 V voltage converter using...
16. ### Adjustable Voltage Regulator Output Voltage Range

Homework Statement FIGURE 2 shows an adjustable voltage regulator using the LT1083 .The LT1083 develops a 1.25V reference voltage between the output and the adjust terminal. By placing a resistor R1 between these two terminals, a constant current is caused to flow through R1 and down through...
17. ### Engineering Basic circuit operation of voltage regulator

Homework Statement Homework EquationsThe Attempt at a Solution I need to know if my understanding of this circuit is correct in terms of R1, R2, Q1, Q2. R1 is a sensing resistor and when Q1 senses a voltage drop at its base, it switches on and passes current around the regulator. I think...
18. ### Voltage Regulator: TR1 & TR2 Current Regulation

Homework Statement https://physicsforums-bernhardtmediall.netdna-ssl.com/data/attachments/66/66455-bb02bb0d3c839e914352eb0379b453f2.jpg Homework EquationsThe Attempt at a Solution Transistors TR2 and TR1 amplify the current being regulated through the regulator. The current gain of...
19. ### Why is the voltage regulator waveform identical to the diode bridge waveform?

I am doing a homework problem for my Power Electronics class. I have attached the relevant image. My question is, (referring to the TOP plot) why is the voltage regulator waveform (purple curve) identical to the voltage waveform coming from the diode bridge (green curve)? Shouldn't it be the...
20. ### Voltage Divider vs Voltage Regulator?

I have two questions. 1. A lot of voltage dividers are wired up like this: Is there any reason why they can't be wired up like below? 2. When should a voltage regulator be used instead of a voltage divider?
21. ### Dramatic voltage drop at voltage regulator output

First time posting a problem on here. Be gentle on me :) So I ran into this problem when I was testing the power supply block for my senior project.I attached a pic...
22. ### Solving for the resistance in a Voltage Regulator

Homework Statement Create a 15V regulated power supply capable of providing a maximum load current of 25 mA. Circuit looks like this: http://i.imgur.com/fMtscbG.png?1ILmax (maximum load resistance) = 25mA Izt (test current) = 20mA Izk (knee current) = 25mA rz = 11 Ω Vz (nominal zener voltage...
23. ### Voltage Regulator w/ Zener Diodes

Homework Statement The diagram: http://images.fr1ckfr4ck.fastmail.fm/probB.jpg These zener diodes; Have a test current of 5mA when 6.8V is applied (V_z=6.8V, I_z=5mA) Have an incremental resistance (r_z) of 20 ohms Knee current (I_zk) is 0.2mA Calculate the output voltage...
24. ### How to build a good voltage regulator

I want to make a .00 to 1.00 volt dc voltage regulator with a pot that goes full circle like 0 volt way to left and 1 volt way to the right I can either power this from a 1.5 AA battery or 12 volt car battery how is the best way to go about and what components would be needed? What I am trying...
25. ### PSPICE rectified AC to voltage regulator

I'm using a LM[Three-One-Seven] to regulate dc voltage output from mains power(240V ac). For PSPICE simulation, I was instructed to use an ideal OpAmp and Darlington BJT to model the IC in PSPICE. I came up with the following model, which satisfies the equation Vo=Vref(1 + RL/RH), where Vref =...
26. ### Where can I find a replacement for LM4040BIZ-10.0 voltage regulator?

I am trying to replace a voltage regulator with an, as of yet, unavailable LM4040BIZ-10.0. I would like to keep the same pin design, but can work with a modified connection if I must. I am not a hobbyist, just a guy that likes to keep things working. I went through a few datasheets and must...
27. ### Voltage Regulator for PCB Design - Help Needed

Hi, Thank you for all the help you've been providing, here I go again with another Electrical question: I am designing a PCB and I need a voltage regulator similar to this: http://img191.imageshack.us/img191/6499/n7p3.png but I don't want to use the LM7805 and the LM7905. I am trying...
28. ### What is a Negative Voltage Regulator and How Does it Work in Audio Amplifiers?

So for a power supply project I need a voltage regulator giving me a positive output at around 40v. Obsessively you can not buy these, So i am useing a circuit which consists of a resistor, npn transistor, and zener diode. the positive input goes to the collector of the transistor and through...
29. ### Problem with voltage regulator

So I need to use this LM117t 3.3v voltage regulator and I asumed the pins were the same as most regulators where you have in/ground/ and out. But it is not working that way, does anyone know the in and outs of this regulator or have an alternative?
30. ### Voltage regulator, tweaking capacitor values

Hi, on page 23 of this datasheet (http://www.fairchildsemi.com/ds/LM/LM7805.pdf) the top figure 10 shows a setup for a fixed output regulator, for example suitable for logic chips which need a steady 5V. I was wondering how critical the values of capacitance were for C1 especially and also C0...
31. ### What am I missing in this voltage regulator design?

The above (top) design is one for a adjustable regulated voltage using an IC. The bottom schematic is the actual design of the IC regulator. My question is, am I missing an obvious way to derive the relationship for Vo? How does this design work, anyway? I figured it had something to do...
32. ### Zener diode as voltage regulator.

The following link is a picture of my zener diode set up with variable load resistor. The Source is 15VDC and the first resistor is a constant 330 ohm. When I use 470ohm up to 15Kohm for the Load resistor RL, I get a 6V voltage drop across the diode. However, when I go down to 330 ohm for RL...
33. ### Voltage Regulator Properties and Behavior

Hello, simple question here! When a voltage is regulated down or up in a circuit by, let's say a DC/DC converter, does the corresponding current increase or decrease respectively so that the system remains consistent with the laws of conservation of energy? In other words, I want to know...
34. ### Voltage Regulator, Battery resistance, current

Dear Experts Lets say I have a power source of 9 volts. A 5v output voltage regulator is connected to this power supply. So, input 9 volts, output is regulated to 5volts constant. the output pin is connected to a battery with has a constant internal resistance. Does this mean, because...
35. ### Power supply using a voltage regulator?

I would like to inquire if a voltage regulator maybe used as a power supply to a system. I am not very familiar with EE stuffs so any help would be appreciated :) Our system consists of aluminum metal plates submerged in water. It needs to be supplied with 10A (DC) thru the portion of the...
36. ### Connecting a 5 pin nte7077 voltage regulator

I am working on a circuit. I have an IC bridge rectifier in place for ac to dc conversion at the proper voltage and amperage. I understand that the nte 7077 voltage regulator is for regulating voltage at 110 volts + or - .8 volts @ 1 amp max. This is a 5 pin IC regulator. I do not understand...
37. ### The use of a reversed biased zener diode in voltage regulator

Hello. I asked this question because I am confused of the use of a reversed Zener Diode in voltage regulator even after I built the circuit using MultiSim. I don't understand why we should put a zener diode right there and how it works. I looked at the I-V plot of the Zener diode and I know...
38. ### Why do we need a voltage regulator here?

Hi all Here is the circuit that I will refer to: LINK : http://electronics-diy.com/lc_meter.php Ok my first question, Why do we need a voltage comparator (LM311) there? A voltage comparator compare the + and - voltages and output the difference?? What I want to do is, measure the inductance...
39. ### Voltage regulator (from power supply) capacitor values?

Hello our doctor gave us a project to design a power supply which looks like this http://i541.photobucket.com/albums/gg395/healing1000/powersupply.jpg however at the voltage regulator part (78xx and 79xx) there are 2 capacitors (the 2 on the right) which I don't know how to find their values...
40. ### Reverse Biasing a Voltage Regulator

Hello All, Simple question here. I have a microcontroller development board that plugs into the wall and has a garden variety LM7805 type 5V regulator on the board for powering the microcontroller and other peripherals. But also on this board is a header that allows the 5V from the board to...
41. ### Voltage regulator to maintain constant amps

I am trying to design a circuit that has 20 mA acoss an LED, I had been advised I could use a voltage regulator to keep the current at 20 mA. However, I am not exactly sure as to how to set up the circuit. Would I set it up so that it would maintain a voltage and then run that voltage across a...
42. ### Fixed voltage regulator problem

Why does LM7805 and LM7809 give less voltage? Practically LM7805 is giving 4.9V instead of 5 and 7809 is giving 8.8V. Can anyone please tell me the reason?
43. ### Which voltage regulator is the best choice for a power supply?

Can anyone tell me which voltage regulator is better to use for power supply. LM140, LM340 or LM78xx series? I want to know which one is most economical and easily availabe. Thankyou
44. ### What is the Best Voltage Regulator for a Dual Polarity Power Supply?

I want to make a power supply which gives DC voltage from -17V to +17 volt, i.e of both polarities. Someone please tell me which voltage regulator is easiest and most appropiate to use? Thankyou!
45. ### What's the difference between a buck converter and a voltage regulator?

Both converts higher DC voltage to lower ones, no? Thanks for answering. =)
46. ### Zener diode as voltage regulator

Homework Statement revered members, this circuit i have attached is for voltage regulation using zener diode. applying kirchhoffs current law i get current through resistance R is IR=IZ+ IL And the voltage drop across the resistance R is V-VOUT HOW this equation of voltage drop is...
47. ### Need Help creating a voltage regulator

Need to create voltage regulator, using a sinusodial wave and a 12 V dc source in series and a load resistor 200 ohms. Voltage output must be 5.7 I Can use op amps, resistors, capacitors, and inductors I have been working at this for weeks and I can not find any information on how to...
48. ### Voltage regulator for cooling fan

Hey all, I am working on a 0-40V variable power supply right now, and while the power supply is working I am wondering if it is in danger of overheating. I am using a LM317 with a 0-5k potentiometer between adjust and ground, and a 165ohm resistor between output and adjust. Input is regulated...
49. ### Single Op Amp as a voltage regulator?

Hello all. I was just wondering if it is possible to use an inverting opamp configuration with feedback to regulate an output voltage V0 without the use of BJT's? For example, the following sketch: http://img411.imageshack.us/img411/2389/opamp.png V0 = Vs * (R1-R2) /2R1 Mathematically, V0...
50. ### Detailed circuit with explanation on the automatic voltage regulator

I want a detailed circuit with explanation on the automatic voltage regulator for synchronous generators if anyone has